The present invention relates to a similarity calculation device, a similarity calculation method, and a program.
Conventionally, as technology for matching patterns such as images, template matching technology of images is known. This technology divides a template image into block areas, performs template matching for each of the block units, and determines the amount of displacement which can obtain the maximum matching ratio within the image to be searched regarding the respective blocks. Template matching is performed by scoring a matching ratio or the like to the coordinates of a scoring space corresponding to the amount of displacement and detecting the peak in the scoring space.
Nevertheless, when a geometric transformation occurs; for instance, when the image to be searched rotates relatively in relation to the template image, the amount of displacement which can obtain the maximum matching ratio will change pursuant to the geometric transformation. In particular, with rotational fluctuation, since the amount of displacement associated with the geometric transformation will differ based on the position, the scoring position in the scoring space will change, and the peak in the scoring space will no longer be steep, and become dull. Consequently, the matching accuracy will deteriorate.
An example of an image matching method which gives consideration to the change in the amount of displacement associated with the geometric transformation described above is disclosed in Patent Document 1.
Patent Document 1 discloses an image matching processing method comprising processing of cutting out a plurality of characteristic local regions from an input image and a model image, respectively, processing of projecting image information of the selected local region on a point set in a feature space, processing of searching, for each local region of one image, for a local region of another image that is projected on a position that is closest to the local region of the one image in the feature space, and associating the local regions, geometric transformation parameter estimation processing of estimating the geometric transformation parameter between the input image and the model image based on the positional relationship of the associated local region of one image and the local region of the other image, and processing of performing geometric transformation to the image information of the local region of one image or the image information of the overall image by using the estimated geometric transformation parameter, and evaluating and matching the consistency of the associated local regions.
[Patent Document 1] Patent Publication JP-A-2001-92963
Nevertheless, with the image matching processing method described in Patent Document 1, since geometric transformation is performed to the image information of the local region of one image or the image information of the overall image by using the estimated geometric transformation parameter, and the consistency of the associated local regions is evaluated, computation for performing geometric transformation to the image information and computation for associating the local regions of the transformed images and calculating the similarity are required, and the amount of computation will increase considerably.